About Physics travelling

Question

A hockey puck is traveling at 12.5 m/s on a floor. The coefficient of friction is 0.15 so how far will it travel before coming to a stop?

Answer 1

For a horizontal floor and no forces other that gravity, the normal force is equal to the weight of the puck

N = mg

For motion, friction is equal to the kinetic coefficient of friction x the normal force:

F = µN = µmg

For no change in potential energy, the initial kinetic energy + the work done = final kinetic energy

KE₁ + U₁₂ = KE₂

The work done is simply negative as the displacement and friction are in opposite directions:

m v₁² /2 + (-Fd) = 0

m v₁² /2 + (-µmgd) = 0

d = v₁² / (2μg) = 12.5²/(2 • 0.15 • 9.81) = 53.1 m